Officials face battle to prevent cities from overheating

With ongoing heatwaves affecting many parts of the planet, bringing soaring temperatures to Europe, as well as the Middle East, Australia, Canada and the US, city officials are scrambling to cope with the impacts on infrastructure and populations.

Scientists are warning that record-breaking heatwaves will become more frequent – and costly – as climate change continues to disrupt weather patterns. A 2017 study1 stated that by the end of the century, three quarters of the world’s population could be subjected to levels of heat and humidity associated with deadly heatwaves for at least 20 days a year if greenhouse emissions continue to rise at current levels.

“What was once regarded as unusually warm weather will become commonplace – in some cases, it already has.”, says Dr Friederike Otto, deputy director of the University of Oxford’s Environmental Change Institute. “This is something that society can and should prepare for,” he warns.

Heatwaves pose significant risks to cities, which are home to more than half the world’s population. Built-up areas get hotter than surrounding rural areas. According to the US Environment Protection Agency the annual mean temperature of a city of a million people or more is 1-3oC warmer on average than its surroundings. By the evening, the difference can be as much as 12oC – a phenomena known as the “heat island” effect.

Heatwaves pose a wide range of threats to cities, including interruptions to water supplies, power outages, and disruption to transport infrastructure, including the melting of roads and railway lines. They also place additional burdens on emergency services, which must respond to heat-related illnesses and deaths, as well as fires.

The latest Lloyd’s City Risk Index quantifies the costs of these heatwave-related threats to the economic output of 279 of the world’s largest cities. The index finds they stand to lose more than $1.77bn of GDP on average every year as a direct result of heatwave-related issues.

New York is the city most at risk in the index, with $190m at risk every year on average, reflecting the size of the population, and the amount and type of high-value assets based there. The US has six cities in total of the top 10 cities in the index at risk from heatwave-related threats, with Chicago, Dallas, Washington, Philadelphia and Los Angeles joining the Big Apple. Paris is at number two on the list, with $90m at risk, Shanghai and Tokyo each have $70m risk, with London 10th at $5m.

Though climate change is considered the root of the increase in heatwaves, it is the design of cities and their infrastructure that is exacerbating their effects. Many cities are built primarily of concrete, with dark-coloured roofs that absorb the sun’s radiation, and which, in turn, heat the surrounding areas.

City planners are now considering what they can do to reduce the impacts of heatwaves – and often the solutions are surprisingly simple.

In Los Angeles in July 2017, the temperature hit 36.60C, breaking a 131-year-old record. To combat the effects of heat, city planners have been carrying out an experiment, painting some of its streets white to try to keep the city cool. Dark coloured or black asphalt absorbs up to 95% of the sun’s rays and can heat up a city’s streets to 650C. The specialist paint, which lasts up to seven years and costs around $40,000 per mile, reflects more of those rays, thereby preventing road surfaces from becoming so hot. This reduces the amount of reflected heat on to nearby buildings, reducing the street temperatures by about 80C, saving on air conditioning costs and helping to reduce the overall temperature of the city.

In India, one simple but counterintuitive solution has been to turn down the air conditioning. This reduces the amount of heat generated by the air-conditioning units, heat that would otherwise add to the overall temperature of the city.

With health issues related to heatwave also a major concern, many cities are implementing heat action plans to help their citizens prepare for and endure extremes of heat.

Chicago in the US was hit by a crippling heatwave in 1995, which saw temperatures hit 410C. It claimed the lives of 739 residents in a single week, most of whom lived in poorer districts. By the time the city experienced the next heatwave, four years later, the city had become far better at protecting vulnerable people, working closely with local media to issue warnings to raise public awareness, and calling upon the public to help old, frail and isolated neighbours to stay cool. City officials now have a database of people who need special services and during a heatwave, phone elderly residents or send police personnel to check in on them.

In Ahmedabad in India, the first city in south Asia to proactively implement a heatwave plan, people are informed of heat-related health risks and given tips on how to minimise them, via text messages as well as broadcast and print media. Alerts are also shared with relevant government and non-governmental agencies to ensure they coordinate their responses. Practical steps include providing water and shade to workers, and changing work shifts to favour cooler hours.

Increasingly, city planners worldwide are also mindful of the need to create green spaces and bodies of water within urban areas which, among other benefits, help to reduce the “heat island” effect.

With more sophisticated weather forecasting techniques, heatwaves, unlike some other natural catastrophes, can be predicted ahead of time and plans implemented to reduce the impacts on human health and infrastructure. These plans can include insurance and reinsurance programmes, which can cover interruptions to a range of city and business functions. For example, the Lloyd’s market offers cover for perils arising as a consequence of heatwaves, including business interruption, public liability, workers’ compensation, property and casualty products and event cancellation.

This blend of planning solutions and financial instruments will need to be further developed if cities are to reduce the risk heatwaves pose to economies and communities, work which will require increasingly close collaboration between planners, city officials and insurers.

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